1. Technical Field
The present invention relates to a halftone mask, a method of manufacturing the halftone mask, and a method of manufacturing an array substrate using the halftone mask. More particularly, the present invention relates to a halftone mask having different light-transmittances by in areas, a method of manufacturing the halftone mask, and a method of manufacturing an array substrate using the halftone mask.
2. Description of the Related Art
Generally, a display device displays images by converting electronic data into a visible image, which is processed by an information processing device. Various types of display devices include, but are not limited to cathode ray tubes (CRT), plasma display panels (PDP), liquid crystal display (LCD) devices, and organic light-emitting diode (OLED) display devices.
An LCD device may display images by using liquid crystal, and electrical and optical characteristics of the liquid crystal vary in response to an electric field applied thereto. The LCD device has been widely used in various electronic devices, because the LCD device has many benefits, such as, for example, light weight, thin thickness, low power consumption, etc., in comparison with other types of display devices. The LCD device may include an LCD panel and a backlight assembly providing the LCD panel with light.
The LCD device may include an array substrate, a color filter substrate and a liquid crystal layer interposed between the array substrate and the color filter substrate.
The array substrate may include a plurality of gate lines, a plurality of data lines, a plurality of thin-film transistors (TFTs), a plurality of pixel electrodes and a first alignment layer. The TFT may be formed in a crossing area of the gate line and the data line to perform as a switching element. The pixel electrode may be electrically connected to the TFT. The first alignment layer may be formed to cover the gate lines, the data lines, the TFTs, and the pixel electrode. The gate lines and the data lines may receive a plurality of signals from driving circuits through each of pad parts, respectively. The TFT may provide the pixel electrode with a pixel voltage signal provided from the data line in response to a scan signal provided to the gate line.
The color filter substrate may include a plurality of color filters, a black matrix, a common electrode and a second alignment layer. The color filers may be formed by liquid crystal cell units. The black matrix may be formed between the color filters. The black matrix may reflect external light. The common electrode commonly may provide a reference voltage to the liquid crystal cells. The second alignment layer may be formed to cover the color filters, the black matrix and the common electrode.
To manufacture the LCD panel, each of the array substrate and the color filter substrate is manufactured, the array substrate and the color filter substrate may be combined with each other, and then liquid crystal molecules may be disposed between the array substrate and the color filter substrate.
Recently developed array substrates have been manufactured by using four masks. The array substrate using four masks includes a data line, a channel layer electrically connected to the data line, a drain electrode electrically connected to the channel layer, and a storage capacitance electrode for maintaining an image for one frame. In the LCD panel manufactured by using four masks, a plurality of semiconductor patterns remains. The semiconductor pattern may include an amorphous silicon (a-Si) pattern under the storage capacitance electrode and an amorphous silicon (a-Si) pattern doped with ions at a high concentration.
When fewer exposure masks are used in processes for manufacturing the display substrate, time and costs for manufacturing the display substrate may be reduced and productivity may be enhanced. Recently, a process for manufacturing a display substrate by using three masks has been developed.
The process using three masks uses a first mask to form a gate pattern, a second mask to form a semiconductor pattern and a source pattern, and a third mask to pattern a passivation film to expose a contact part. A pixel electrode is formed through a lift-off method. The passivation film is patterned through two dry-etching processes.
As the size of an LCD panel increases, the manufacturing cost and failure rate of an array substrate having TFTs formed thereon may increase. To decrease the manufacturing cost and the failure rate, a halftone mask which may be alternated with a conventional slit mask has been developed.
In comparison with the slit mask, the halftone mask may readily control the thickness of a remaining photoresist pattern (rTPR) after a mask process.